Completeness of outcome description in studies for low back pain rehabilitation interventions: a survey of trials included in Cochrane reviews

Background Selection of appropriate outcome measures is crucial in clinical trials in order to minimize bias and allow for precise comparisons of effects between interventions [1-3]. Objective We aimed to assess the frequency and completeness of outcome measures in randomized controlled trials (RCTs) included in Cochrane systematic reviews (SRs), focusing on evaluations of the efficacy and safety of rehabilitation interventions for mechanical LBP. Materials and methods We performed a cross-sectional study of all RCTs included in all Cochrane SRs (full-text) published on The Cochrane Database of Systematic Reviews in February 2013. Two authors independently evaluated the type and frequency of each outcome measure reported in the fulltext of RCTs, the methods used to measure outcomes, and the proportion of outcomes fully replicable based on the reported information (Figure 1). Results Our literature search identified 11 Cochrane SRs, including 185 RCTs. Across all RCTs, thirty-six different outcomes were investigated. The outcomes most commonly reported were pain (165/185; 89,2%, 95% Confidence Interval (CI) 84.7% – 93.7 %), disability (118/185; 63,8%, 95% CI 56.9% – 70.7 %), range of motion (72/185; 38.9% 95% CI 31.9% – 45.9%), and quality of life (45/185; 24,3%, 95% CI 18.1% – 30.5%) measured respectively by 70, 43, 41, 19 different measurement instruments (Figure 2). The procedure of blinding assessment was reported in 49.7% of the RCTs for pain (n= 82 RCTs) and 45% of RCTs for disability (n=53 RCTs). Pain, disability, range of motion, and quality of life outcomes were reported as fully replicable in 10.3% (n= 17 RCTs), 10.1% (n= 12 RCTs), 5.5% (n= 4 RCTs), and 6.6% (n= 3 RCTs) of the RCTs, respectively (Figure 3). Conclusions A large number of outcome measures and a myriad of measurement instruments were used across all RCTs. The reporting was largely incomplete, suggesting better opportunities for the standardization of approaches and reporting.